A conventional cylinder generally includes a cylinder with a piston movably received therein and the outer diameter of the piston is substantially the same as the inner diameter of the cylinder so that the interior of the cylinder is divided into two rooms by the piston. The movable piston changes the room so as to transfer the pressure that the pressurized air or hydraulic liquid pushed by the piston. The piston decides the transfer of the force of the cylinder.
The cylinder usually is a hollow and cylindrical body and the piston includes piston rings mounted thereon which are in contact with the inside of the cylinder so that when the piston moves, the volume of the rooms in the cylinder changes.
Taiwan Patent Application No. 092204057 discloses a bicycle shock absorbing device which includes an outer tube with a closed end and an open end in which a cylinder is inserted. The cylinder has an open end inserted into the outer tube and fixed with a fixed member, and the other end of the cylinder extends out from the outer tube and is sealed. A piston rod extends through the closed end of the outer tube and is connected with a piston which is located in the cylinder. The piston includes a valve hole for receiving a valve therein. The piston defines the interior of the cylinder into the first room and the second room, the first room is located close to the closed end of the outer tube and a movable member is located between the fixed member and the piston. There is a gap defined between the movable member and the fixed member.
Taiwan Patent Application No. 099209955 discloses a bicycle shock absorbing device discloses an outer tube with an inner tube received therein, and a top cap and a bottom cap respectively seal the two ends of the outer tube. A room is defined between the inner tube and the outer tube, the inner tube communicates with the room. The room includes a piston received therein which is movably in contact with the outside of the inner tube and the inside of the outer tube. Hydraulic liquid flows between the inner tube and the room and sealed by the movable piston. Air is filled in the room and sealed by the movable piston so that the piston is balance between the pressures of the air and the hydraulic liquid.
For Taiwan Patent Application No. 092204057, the movable member is connected with the piston rod and the first room and the gap are defined by the movable member, the piston and the fixed member. For Taiwan Patent Application No. 099209955, the movable piston is movably in contact with the outside of the inner tube and the inside of the outer tube, and the movable member in the room defines two respective rooms for receiving hydraulic liquid and air.
However, no matter the cylinder is connected with a piston rod or between two tubes, the piston rings are located on the outside of the piston so that the outside of the piston are applied by linear forces when the piston moves. This makes the piston to be tilt and gaps are defined between the cylinder and the piston to affect the sealed status. Therefore, the hydraulic liquid and/or air in one room may flow into the other room to affect the movement of the piston. Besides, the outer diameter of the piston restricts the size of the cylinder so that when a smaller cylinder is required, the size piston has to be reduced and which is difficult.
The present invention intends to provide a cylinder assembly which improves the shortcomings of the conventional cylinders.